Cold Air Distribution in Office Buildings: Technology Assessment for California

Abstract

This paper presents the results of a study to assess the current state of practice, and energy and operating cost implications of cold air distribution in California, and to identify the key research needs for the continued development of this technology in new commercial buildings in the state. Whole-building energy simulations were made to compare the energy performance of a prototypical office building in three California climates using conventional and cold air distribution, with and without ice storage, to show the impacts of load shifting, energy use, and utility costs for three typical utility rate structures. The merits of economizers and fan-powered mixing boxes were also studied when used in conjunction with cold air delivery. A survey was conducted to assess the perceived strengths and limitations of this technology, perceived barriers to its widespread use, and user experience. The survey was based on interviews with consulting engineers, equipment manufacturers, researchers, utility representatives, and other users of cold air distribution technology. Selected findings from the industry survey are also discussed. Cold air distribution (CoAD) is found to always reduce fan energy use in comparison to conventional 55 F (13 C) air distribution systems, when conditioned air is delivered directly to the space (no fan-powered mixing boxes). Total building energy use for ice storage/CoAD systems was always higher than a well-designed conventional system, but significantly lower than a commonly-installed packaged system. When a favorable utility rate structure was applied, the load-shifting benefits of ice storage/CoAD systems produced the lowest annual operating costs of all system-plant configurations studied.